msw: Implement mswSession model

Author: Turbo87

packages/crates-io-msw/models/index.js

@@ -1,5 +1,7 @@
+import { mswSession } from './msw-session';
 import { user } from './user';
 
 export const models = {
+  mswSession,
   user,
 };

packages/crates-io-msw/models/msw-session.js

@@ -0,0 +1,24 @@
+import { oneOf, primaryKey } from '@mswjs/data';
+
+import { applyDefault } from './-utils';
+
+/**
+ * This is a mirage-only model, that is used to keep track of the current
+ * session and the associated `user` model, because in route handlers we don't
+ * have access to the cookie data that the actual API is using for these things.
+ *
+ * This mock implementation means that there can only ever exist one
+ * session at a time.
+ */
+export const mswSession = {
+  id: primaryKey(Number),
+  user: oneOf('user'),
+
+  preCreate(attrs, counter) {
+    applyDefault(attrs, 'id', () => counter);
+
+    if (!attrs.user) {
+      throw new Error('Missing `user` relationship');
+    }
+  },
+};